A communication or data communication or signal communication is required between an electronic engine control unit and an electronic transmission control unit in modern motor vehicles with an automated transmission system such as, for example, an automated shift transmission (ASG) or parallel shift transmission (PSG).
Critical situations may develop in these systems, especially with regard to safety. This happens, for example, in case of a total failure of the electronic transmission control unit, which, for example, can be caused by a processor failure.
One measure that is known—at least in-house in the applicant's establishment—in order to prevent or reduce the occurrence of situations that are critical in terms of safety or behavior forms that are critical in terms of safety in such situations consists in using a redundant processor. Such a system, for example, can be a so-called ISM (Integrated Safety Monitoring System). A second processor or redundant processor is provided here and it, for example, has a lesser capacity when compared to the main processor. The redundant processor and the main processor monitor each other, the system being shut off if one of these processors determines a problem with respect to the other processor. Shutting the system off in this kind of design, as a rule, results in a situation where all gear and clutch actors or actuation systems are frozen specifically in their particular current position. This strategy might possibly be considered a good compromise for at least many situations. In this strategy, one assumes that when the starting clutch is engaged during the freezing phase and when the gear is engaged in the gearbox device, the driver always has the possibility of braking or stopping the vehicle with a brake, in particular, service brake; furthermore, in this strategy, one starts with the assumption that when the clutch device is disengaged during the freezing phase, the vehicle can also be braked or brought to a stop by the driver by means of the brake or the service brake; furthermore, in this strategy, the assumption is that the vehicle can also be brought to a standstill by the driver when no gear is engaged in the transmission device during the freezing or when it is in a neutral position.